Why on earth would you need a "land line?" A cell phone is all you need, nothing more.

Apparantly you are. I happen to live in one.

don’t trust them any further than I could throw the whole lot of them.

Have you tried looking on YouTube? There are tons of helpful, surprisingly brand & model specific videos for troubleshooting. Your exact issue might be on there.

A 2014 phone does not sound like “reached the end of it’s life” to me. Sounds like Comcast bs.

Good luck!

if you can borrow one. Any phone should work, telephone signals on land lines have been the same practically forever. The last change was mostly dropping pulse dialing.
It's unlikely that your phone would work only after resetting the modem.

if you want emergency vehicles/personnel to find you in an emergency.

Relative, fireman, said that cells wont help them find you if for some reason you cant give them the location.

have VoIP--one of which is that it's thrown in free when you bundle with other services.

I had comcast in the past.
I had a modem from when I bought my house 11 years ago until 3 years ago. In the 18 months after that I had 3 different "newer" "better" modems which crapped out within months install.
I gave up on comcast.

IMO you have an intermittent problem that has to do some handshaking between the modem and the cordless base unit. If you have no alternative to comcast, you could install a small UPS that would keep both units alive in the event of momentary power drops.

I had something similar to this:
https://www.newegg.com/cyberpower-cp350slg-nema-5-15r/p/N82E16842102135

Personally, I would tell comcast to unbundle the VOIP demand they cut your bill by the amount they charge for VOIP and switch providers:
https://www.zdnet.com/article/best-voip-providers/

About 90% of support techs in many industries have little technical training and mostly rely on a script to guide them.
Trying to get one of these guys to realize that an intermittent problem may actually be a problem that they can't verify is a losing battle.

Assuming your Panasonic phone is a normal wired or cordless POTS phone (plane old telephone service), and not a native VoIP phone, then there really is nothing that would "reset" your phone when you reset your cable modem.

So my advice ... the next time it fails:

1) power cycle and/or replug in your phone first. See if that restores service (I would be pretty darn surprised...).

2) check to see if your internet access has also gone out. I.e. assuming your cable modem provides WiFi, connect to your WiFi with your cell phone and/or a computer and see if the internet is working. On your cell phone you might need to turn off "data" access over the cell network to be sure your network connections are using WiFi. Otherwise they could be trying to use WiFi, failing, and then switching back to data over cellular without your noticing.

3) see if you can make outgoing calls from your phone.

4) and of course, see if trying a different phone works before resetting the modem.

And I'll second the motion about having a small UPS to keep the power to the cable modem cleaner. A lot of gear like this gets confused with power glitches. Of course, it might not help you at all depending on the root cause of your outages.

My mother has had similar problems. Every time her (DSL) Internet goes down, she loses her VoIP phone access as well. She had no idea. Some sales person talked her into VoIP without her realizing she was giving up her landline.

Good luck!